Proper way to handle "alias this" deprecation for classes

[Chris Piker]

Hi D

One of the dependencies for my project has a class that makes use 
of the `alias x this` construct.  According to dmd 2.103, alias 
this is deprecated for classes, so I'd like to correct the 
problem.

Is there a specific paragraph or two that I can read to find out 
what is the appropriate replacement construct?  On a related 
note, has anyone created a code maintenance guide to help 
work-a-day programmers navigate recent changes to the D language?

For reference, here's a the code in question (from dpq2, 
result.d):
```d
package immutable final class ResultContainer
{
     version(Dpq2_Dynamic)
     {
         import dpq2.dynloader: ReferenceCounter;

         private ReferenceCounter dynLoaderRefCnt;
     }

     // ResultContainer allows only one copy of PGresult* due to 
avoid
     // double free. For the same reason this class is declared as 
final.
     private PGresult* result;
     alias result this;       //<---- Deprecation Warning Here
     package this(immutable PGresult* r)
     {
         assert(r);

         result = r;
         version(Dpq2_Dynamic) dynLoaderRefCnt = 
ReferenceCounter(true);
     }

     ...
```

Thanks for any pointers,